Build fails with "couldn't find a square icon to use as AppImage icon" for commands like pnpm tauri:debug

[dbarnett]

When I run pnpm tauri:debug or pnpm tauri:build on a fresh checkout of the tablex repo, I get an error about missing icons:

❯ pnpm tauri:debug

> tablex@0.1.0 tauri:debug /home/david/projects/tablex
> pnpm --filter @tablex/core exec tauri build --debug

     Running beforeBuildCommand `npm run build`

> @tablex/core@0.3.1 build
> next build

   ▲ Next.js 14.0.2

 ✓ Creating an optimized production build    
 ✓ Compiled successfully
 ✓ Linting and checking validity of types    
 ✓ Collecting page data    
   Generating static pages (0/8)  [=   ] ⚠ Entire page /dashboard deopted into client-side rendering. https://nextjs.org/docs/messages/deopted-into-client-rendering /dashboard
 ⚠ Entire page /dashboard/details deopted into client-side rendering. https://nextjs.org/docs/messages/deopted-into-client-rendering /dashboard/details
 ✓ Generating static pages (8/8) 
 ✓ Finalizing page optimization    

Route (app)                              Size     First Load JS
┌ ○ /                                    1.61 kB         111 kB
├ ○ /_not-found                          871 B          85.4 kB
├ ○ /connect                             8.12 kB         164 kB
├ ○ /connections                         4.19 kB         143 kB
├ ○ /dashboard                           175 B          89.7 kB
└ ○ /dashboard/details                   25.8 kB         175 kB
+ First Load JS shared by all            84.5 kB
  ├ chunks/399fa1b5-64be7eb8847af37b.js  53.3 kB
  ├ chunks/51-359ff64d79f27c7c.js        29.3 kB
  ├ chunks/main-app-acc7200bd005946d.js  219 B
  └ chunks/webpack-dd335d907f2bea33.js   1.69 kB


○  (Static)  prerendered as static content

   Compiling tauri v1.5.4
   Compiling tauri-macros v1.4.3
   Compiling table_x v0.1.0 (/home/david/projects/tablex/apps/core/src-tauri)
    Finished dev [unoptimized + debuginfo] target(s) in 15.13s
    Bundling table-x_0.3.1_amd64.deb (/home/david/projects/tablex/apps/core/src-tauri/target/debug/bundle/deb/table-x_0.3.1_amd64.deb)
thread '<unnamed>' panicked at /build/tooling/bundler/src/bundle/linux/appimage.rs:73:6:
couldn't find a square icon to use as AppImage icon
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Seems to be tauri-apps/tauri#749. The other pnpm tauri:dev command runs fine.